Modern motorcycles and bicycles with front suspension systems are equipped universally with a fork type system. Such a system includes a pair of telescopic tubes that are inverted one inside the other and contain internal springs or springs and dampeners. The fork tubes are connected through a head assembly to a freely rotating steering column that is attached to the main frame of the vehicle. An axle for the front wheel is fixed perpendicular to the lower ends of said fork tubes. This simple structure is an effective front suspension design but nevertheless suffers from certain disadvantages which have long been recognised but never completely overcome. The main disadvantages associated with this design are, shock loads from the road surface onto the front suspension are directed towards the frame in the vicinity of the steering head area, which is far removed from the centre of gravity of the vehicle, where frame construction is relatively light but the displacing wheel and lower sections of the forks are of considerable mass. This results in shock loads only being partially absorbed and transmits considerable load from the suspension in the direction of the frame, which invariably causes the frame to pitch. There is also a tendency for the vehicle to ‘dive’, or pitch forwards and downwards, during hard braking of the front wheel due to the telescopic forks being raked out where displacement of the front wheel is both upwards and rearwards. Further, with telescopic forks the load path of the shock loads to the frame is convoluted, where the steering head area and associated components have to be substantially stronger and heavier than need be if it were only to accommodate the torque necessary to effect steering.
As a general design principle, it is desirable that weight and road loads be transmitted in the simplest and shortest possible manner in order to minimise the weight of the structures which must transmit and bear these loads. It is further desirable to have the most direct connection between the front wheel axle and the mechanisms used for steering control of the front wheel. It is also desirable to have as few moving components in a suspension system as possible, so to reduce complication, manufacturing costs, and also to reduce the inertia associated with both steering motion and suspension action. It is further desirable for the standpoint of safety to resist excessive diving of the front suspension during front wheel braking. Further, in general, it is desirable to minimise pitching motion at the handlebars.